Steps in Excitation-Contration Coupling

Question 1

Steps in Excitation-Contraction Coupling

Answer 1

1. APs in the axon of a motor neuron case the release of ACh at the neural-muscular junction
2. ACh generates AP in the sacrolemma
3. The AP travels down through the T-Tubles of the sarcolemma.
4. AP in the T-tubes cause the opein of Ca-ion Gates in the near by the terminal cisternae (TC).
5. Ca released from the TC flows into the sarcoplasm and attaches to troponin causing its striation to change.
6. The shape change of troponin causes the ribbon of tropomyosin to shift position and exposes the binding sites on actin to the head of the myosin cross bridge.
7. The cross bridges have been previously activated by the hydrolysis of ATP and now bind to actin.
8. Once the cross bridge attach to the actin and power stroke occurs pulling the actin over the myosin.
9. A new ATP can now attach to myosin allowing it to detach from action re-extend and repeats steps 7 & 8 as long as AP keep coming down the T-Tubes and Ca remains attached to trop in.
10. When AP stop the Ca-gates close and Ca is quickly pumped out of the sarcoplasm back into the sarcoplasmic reticulum by primary active transport mechanism. Tropomyosin falls back into place and the muscle relaxes.

Question 2

Step 1 of Excitation

Answer 2

1. APs in the axon of a motor neuron case the release of ACh at the neural-muscular junction

Question 3

Stept 2 of Excitation

Answer 3

2. ACh generates AP in the sacrolemma

Question 4

Step 3 of Excitation

Answer 4

3. The AP travels down through the T-Tubles of the sarcolemma.

Question 5

Step 4 of Excitation

Answer 5

4. AP in the T-tubes cause the opein of Ca-ion Gates in the near by the terminal cisternae (TC).

Question 6

Step 5 of Excitation

Answer 6

5. Ca released from the TC flows into the sarcoplasm and attaches to troponin causing its striation to change.

Question 7

Step 6 of Excitation

Answer 7

6. The shape change of troponin causes the ribbon of tropomyosin to shift position and exposes the binding sites on actin to the head of the myosin cross bridge.

Question 8

Step 7 of Excitation

Answer 8

7. The cross bridges have been previously activated by the hydrolysis of ATP and now bind to actin.

Question 9

Step 8 of Excitation

Answer 9

8. Once the cross bridge attach to the actin and power stroke occurs pulling the actin over the myosin.

Question 10

Step 9 of Excitation

Answer 10

9. A new ATP can now attach to myosin allowing it to detach from action re-extend and repeats steps 7 & 8 as long as AP keep coming down the T-Tubes and Ca remains attached to trop in.

Question 11

Step 10 of Excitation

Answer 11

10. When AP stop the Ca-gates close and Ca is quickly pumped out of the sarcoplasm back into the sarcoplasmic reticulum by primary active transport mechanism. Tropomyosin falls back into place and the muscle relaxes.